The disk parts whose radial dimension is generally larger than axial dimension are common typical parts in machine parts, and have high precision requirement for end beat, cylindricity of the inner hole, the circular runout and the total run-out of the cylindrical surface. The axial reference of the disk part is the two ends, and the radial reference is the axis determined by the cylinder surface of the inner hole. Due to the mandrel has machining errors and the installation eccentricity error, when taking the inner hole as datum to machine the external cylindrical surface, it is difficult to guarantee the coaxiality of the external cylindrical surface and the datum cylindrical surface of the inner hole. Even though the roundness error of external cylindrical surface is smaller, the larger circular runout and larger total run-out of cylindrical surface of the disk part would be produced due to the concentricity errors of the inner and the external cylindrical surface.
The typical products of the disk parts include bearing encloses, friction wheels, base circle plates of the reference level involute measuring apparatus, the reference disks of roundness instrument and so on. In the field of measurement, the accuracy requirement of the disk part used as a datum for roundness is to submicron or nanometer level. The current machining equipment and ultra-precision grinding process cannot meet the processing requirements of such disk part. Lapping is a kind of ultra-precision machining processing, which is mainly used for machining plane, cylindrical surface and spherical surface. At present, the flatness of plane lapping can be attained to 0.2˜0.5 μm. The roundness of cylindrical lapping can be attained to 0.2˜0.5 μm and the cylindricity can be attained to 0.5˜1 μm. The ultra-precision lapping technology is used to process class-1 standard optical flat with a diameter of 150 mm and the flatness can be attained to below 50 nm. However, the present polishing processes and devices are only suitable for ultra-precision machining of flat and spherical parts.